Apparatus for transmitting digital signals across a rotary gap

An apparatus is disclosed for coupling digital signals across a rotary mechanical gap as, for example, in a helical scan optical or magnetic tape recording/playback system where it is required to couple digital signals having a wide range of pulse widths between the stationary portion of the system and the rotating headwheel. The apparatus includes a rotary transformer comprising inductively-coupled first and second coils located, respectively, in the stationary and rotating portions. A capacitor positioned between the signal source and the primary winding of the rotary transformer converts the pulsed digital signals from the source into signals of changing current so that pulses of variable widths are efficiently coupled through the transformer. In this way, digital pulses having width ratios of approximately five-to-one can be transmitted across the gap.